A more thorough explanation:

Definition: In Roman law, an edict or mandate; an ordinance or law proclaimed by the emperor. An edict was a constitution of the emperor acting on his own initiative, differing from a rescript in not being returned in the way of answer; from a decree in not being given in judgment; and from both in not being founded upon solicitation. As an imperial constitution, it had the force of law.

Examples:

• Edictum aedilicium: A curule aedile's edict regarding sales in the public market; esp., an edict giving remedies for sales of defective goods, animals, or slaves.
• Edictum annuum: An edict issued by a praetor at the beginning of the one-year term of office.
• Edictum provinciale: An edict or system of rules for the administration of justice, modeled on edictum praetoris, issued by the provincial governors in the Roman Empire.

These examples illustrate how edictum was used in different contexts within Roman law. The edictum aedilicium was specific to the curule aedile's jurisdiction and dealt with sales in the public market. The edictum annuum was issued by a praetor at the beginning of their term of office and set out the principles by which they proposed to act. The edictum provinciale was a system of rules for the administration of justice in the provinces, modeled on the edictum praetoris.